Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1998-02-06
2001-08-07
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S231100, C429S223000, C423S594120, C423S641000
Reexamination Certificate
active
06270927
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a lithium secondary battery comprising a cathode including a material that can be doped/undoped with lithium ions as an active material; an anode including a lithium metal, a lithium alloy, or a material that can be doped/undoped with lithium ions as an active material; and a liquid or solid electrolyte, and to the cathode active material for use in the lithium secondary battery.
2. Related Art of the Invention
With a rapid advance of portable and cordless electronic devices, demands for a lithium secondary battery which can realize small size, lightweight and a large capacity compared to the conventional secondary batteries have been increasing.
As a cathode active material in a lithium secondary battery, lithiated cobalt dioxide has been studied and it has already been put into practical use in the lithium secondary batteries as a power source for cellular phones and camcorders. Recently, lithiated nickel dioxide using a nickel compound as a raw material which is cheaper than cobalt compound and abundant in terms of resources has been examined actively.
Lithiated nickel dioxide, as well as lithiated cobalt dioxide, is a compound having an &agr;-NaFeO
2
structure. However, it is difficult to synthesize lithiated nickel dioxide compared to lithiated cobalt dioxide, because nickel is easily substituted at a lithium site in lithiated nickel dioxide. Recent progress in the synthetic conditions has offered substantial practicability of stoichiometric composition of lithiated nickel dioxide presenting a high discharge capacity. However, the lithiated nickel dioxide still suffers capacity drop-off associated with repeated cycles of charging/discharging processes at high capacity, or in other words, a poor cycle characteristic.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a lithium secondary battery of a high energy density using a cathode active material having an excellent cycle characteristic in charging/discharging at a high capacity and a small irreversible capacity.
REFERENCES:
patent: 4668595 (1987-05-01), Yoshino et al.
patent: 5591548 (1997-01-01), Mao
patent: 5595842 (1997-01-01), Nakane et al.
patent: 5750288 (1998-05-01), Xie et al.
Miyai Takeshi
Nakane Kenji
Nishida Yasunori
Satoh Tomoari
Chaney Carol
Martin Angela J.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Sumitomo Chemical Company Limited
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